1. Field of the Invention
This invention is in the field of electric motor stator manufacture and more particularly to forming and spreading the windings at an end of the stator to provide clearance for rotation of attachments to the motor rotor.
2. Description of the Prior Art
In electric motor manufacture, the motor stator is wound with wire, coated with insulation, to provide a field in the stator opening in which a rotor is mounted for rotation. Typically, the windings, or end turns, are such as to form a dome over one end of the opening, while the windings, or end turns, at the other end of the opening have been spread to permit access to the opening for insertion of a rotor into the opening. While there is sufficient clearance at the one end to insert a rotor shaft, through the center of the domed winding, in most applications it is necessary to fully spread the windings at the domed end in order to provide clearance for rotation of a fan, or other member, that is secured to the shaft at the domed end.
In prior art devices, a way in which the windings at the domed end are spread is to forcibly insert, from the other end, a resilient, cylindrical plug through the winding dome and then compress the plug along the axis of the opening to enlarge the plug diameter and further spread the windings until they are sufficiently deformed to provide the aforementioned clearance at the one end.
The plug material is typically rubber or a resilient plastic, such as urethane, and thus has a surface with a relatively high coefficient of friction. Upon forcible axial insertion of the plug into the domed winding, prior to plug compression, the windings are dragged in the direction of plug movement due to the frictional force with the plug surface and in the process the insulative coating on the windings is frequently broken, causing arcing and short circuits between the winding coils.
Further, during the axial compression of the plug, the plug bulges, increasing its diameter. As the compression progresses, the bulge diameter moves axially, causing outward abrupt bending of the clamped stator windings, further increasing the likelihood of breaking the insulative coating on the windings and shortening the wire height as it is being spread.